Difficulty in establishing long term human prostatic cancer cell lines in vitro has impeded progress toward the understanding of prostate tumorigenesis and the development of new therapies for prostate cancer. To date only four prostate cancer cell lines, initiated from metastatic lesions, have provided the basis for the majority of in vitro experiments concerning the biological and molecular events regulating prostate tumorigenesis. Accordingly, there is an enormous academic, diagnostic, and therapeutic need for established long-term prostate cancer cell cultures.
In recent years, prostate cancer has emerged as the most commonly diagnosed cancer in men in the United States. In this year alone, new cases of prostate cancer are estimated to approach 300,000 with over 40,000 deaths, resulting in a cancer mortaility rate second only to lung cancer (1). Although prostate cancer mortality commonly results from metastatic disease, nearly 60% of newly diagnosed patients present with localized primary tumors. Surgery and radiation therapy are often effective in treating localized disease, but disseminated metastatic disease is largely untreatable. Despite considerable scientific effort there is still relatively little known about the biological events causing the initiation and progression of prostate cancer. The development of new strategies for the treatment of adenocarcinoma of the prostate necessitates an increased understanding of the cellular and molecular events involved in the generation of primary prostate cancer and its metastatic progression.
Four human prostate cancer cell lines (LNCaP, DU145, PC-3, TSU-Pr1), initiated from metastic lesions, have provided the basis for the majority of in vitro experiments concerning prostate cancer. Extensive progress has been made towards the in vitro cultivation of short-term lines from primary (nonmetastatic) prostate cancers. The advances have included culture media development and improvements in fresh tissue preparation and prostate epithelial cell culture techniques (3,4). However, the establishment and maintenance of long-term human prostate epithelial cell lines from primary tumors has been unsuccessful in the absence of in vitro immortalization. To this end, there exist only a small number of reports describing long-term immortalized cell lines, and these have been limited to normal prostatic epithelial cultures (5,6,7,8). Thus, the goal of the current study was to develop reliable methods for generating continuously proliferating prostate cancer cell lines derived from primary tumors.
Beyond the difficulties inherent in establishing immortal prostate epithelial cell lines are the problems associated with distinguishing cultivated prostate cancer from normal epithelial cells. Past cytogenetic evaluation of multiple short-term prostate epithelial cell cultures has revealed that the majority of lines generated from localized prostate cancers exhibit a normal male karyotype (9,10,11). This, combined with the unremarkable microscopic morphology of short-term cultures and a pervasive lack of success with xenotransplantation, has rendered accurate identification and characterization of human primary prostate cancer cell lines extremely difficult.
The initiation of prostate cancer is believed to occur as a result of multiple genetic changes within the cell, including the inactivation of potential tumor suppressor genes as manifested by allelic chromosomal deletions (reviewed in 12). Early studies examining chromosomal deletions in fresh (noncultured) primary prostate cancer speciments exhibited allelic loss of heterozygosity (LOH) on chromosomes 10q and 16q (13,14,15). Subsequent studies demonstrated a remarkably high percentage of allelic loss on the short arm of chromosome 8, thus moving chromosome 8p to the forefront of the list of potential sites for prostate cancer—associated tumor suppressor genes (16,17,18). Moreover, recent examination of 99 microdissected tumors (19) and 54 micro-dissected PIN lesions (20) for LOH on the short arm of chromosone 8p demonstrated strong evidence for the inactivation of a tumor suppressor gene(s) on chromosome 8p12-21 when compared to matched normal controls. Accordingly, examination of LOH within this minimal deletion region on chromosome 8p12-21 represents a potentially powerful alternative method for the identification and characterization of human prostate epithelial cell lines derived from primary tumors.
The present invention is the successful generation and unique genetic characterization of multiple immortalized human tumor cell lines derived from primary adenocarcinomas of the prostate.